Back-draft damper



Dec. 13, 1927. 1,652,790

I. D. M ORGAN BACK DRAFT DAMPER Filed Dec 18, 1926 2 Sheets-Sheet 1INVENTOR QQFM (6. V W W Dec. 13, 1927.

' I. D. MORGAN BACK DRAFT DAMPER Filed Dec. 18, 1926 2 Sheets-Sheet 2INVENTOR Patented Dec. 13, 1927.

UNITED STATES 1,652,790 PATENT OFFICE.

IRA D. MORGAN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO J.SCOTT MORGAN, OF PITTSBURGH, PENNSYLVANIA.

BACK-DRAFT DAMPER.

Application filed December 18, 1926. Serial No. 155,682.

The invention relates to back draft dampers for use in ventilatingsystems. The flaps employed in dampers of this kind are of thin sheetaluminum, designed to operate from very light air currents, and shouldbe practically noiseless in 0 eration. Heretofore, it has been thepractice to hinge the flaps on metal wires extending transversely of arectangular damper frame, so that the lower edge of each flap engagesthe upper portion of the flap next below. The lower edges of the flapsare provided with felt strips designed to act as silencers and toincrease the effectiveness of the seals between the flaps. These dampershave been more or less unsatisfactory for several reasons. Due to thesagging of the supporting hinge wires, the flaps are liable to rub attheir edges on the supporting frame and make an objectionable noise,which is increased by the vibration incident to the thin shell-likeflaps striking together. Further, the weight of the felts upon the flapsreduces their freedom of movement, thus reducing the flow of air throughthe damper, particularly with a light draft. The present invention isdesigned to overcome the foregoing objections, and has for its primaryobjects, the provision of an improved construction, (1) in which 30there is no sagging of the supports for the flaps; (2) in which theflaps swing freely without any rubbing action on adjacent parts; inwhich the noise incident to one flap striking against another isavoided, and, (4) in which the weight of the felts is removed from theflaps, so that they swing more freely, and thus give a better flow ofair through the damper under light draft conditions than was the casewith the construction heretofore used.

Briefly stated, the foregoing results are secured by providing therectangular damper frame with a series of stiffening bars, to which theflaps are hinged, and which carry rearwardly projecting felt stripsadapted to contact with the swinging edges of the flaps. The barsstiffen the rectangular supporting frame, and in addition, each performsthe dual function of supporting the flap lying beneath, and of holdingthe felt for engaging the flap lying above it. Due to the rigidity ofthe bars and the stiffness of the structure as a whole there is nosagging of the flaps, which always maintain their original freedom ofmovement, thus avoiding any scraping noises incident to the edges of theflaps moving over the supporting frame. The vibration and noise incidentto the flaps engaging the felts is also reduced to a minimum, due to thefirm support of the felts on the relatively rigid transverse bars. Theflaps also swing with greater freedom than those heretofore used,because of their reduced weight incident to the transfer of thefeltsfrom the flaps to the bars. Certain embodiments of the inventionare illustrated in the accompanying drawings, wherein:

Figure 1 is a front elevation. Figs. 2 and 3 are sections respectivelyon the lines IIII and IIIIII of Fig. 1. Fig. 4 is a partial rearelevation on an enlarged scale. 5 and 6 are sections on the lines VV andVIVI respectively of Fig. 4. Fig. 7 is an enlarged section through oneof the trans verse bars. And Fig. 8 is a section through a modifiedformof transverse bar.

The rectangular frame of the damper consists of the sheet metal sidemembers 1, 2, 3 and 4, stiffened on its forward side by the angle 5soldered or otherwise secured to the side members. Suitable cornerstiffeners 5 and 5 are also provided to increase the rigidity of theframe. Extending longitudinally of the frame is the bar 6 of T-crosssection, such bar being secured at its ends to the members 3 and 4.Lying transversely of the frame are the bars 7, 7, 7, etc. soldered attheir outer ends to the members 1 and 2 and at their inner ends to theT-bar 6.

The transverse bars 7 are preferably of the cross section indicated inFigs. 5 and 7, being formed of strips of sheet metal bent double to giveadditional stiffness and to provide the lips 8, 8, and also bent intoangular form which further adds to the stiffness. Between the lips ofeach bar is mounted a strip 9 of soft flexible material, such as felt,such felt strips serving to cushion the impact of the metal flaps aslater described.

Hinged to each of the bars 7 is a flap 10 of very thin light metal, suchas aluminum. Each of the flaps is provided with a pair of clips 11, 11riveted in position and engaging the horizontal portions of the hangers12, 12. The vertical portions of these hangers extend. through the lips8, 8 of ,the bars 7, and through the felt strips 9 lying between thelips, so that the hangers perform the function of retaining the felt inposition. The

Figs.

upper ends of the hangers are bent into the form of eyes to retain themin position. The lower edge of each flap engages the felt strip on thebar next beneath.

The device, as thus constructed, is very rigid, due to the transversebars, and to the stiff construction of the supporting frame. The flapsswing very freely, because of their light Weight and for thie reason andbecause of the stiffness of the Crossbars; the noise and vibrationproduced when the flaps engagetlie felts is reduced to a minimum; The

rigidity of the structure also obviates any eei t e. flas er Q eq eno-uin upoirtlle frame and interference with their movement, stioh as hasbeen common with flat s supported upon transverse wires.

'tig; semen-es 91 211 nu er of o ifiedfoians of transverse bars whichmight l' led; alt h tel} th eneul er s heretgfore'dseri ed is preferred,because of itsgreater stifiness' This bar 13 of Fig. 8 comprises a sheetof metal bent into U-,shape with a felt 14 held between the metal as inthe other forniof lean 1 What'I elaim'isa 11- Ii mhii etie e a a k thefam ree eee t metal f ame ri Qf t ansee a e e e in /9 9 the fr me tspaced intervals, a strip of soft flexible material carried by each barand projecting to the rear thereof, and a flap of thin sheet metalhinged at its upper edge to each of inetalstrip bent upon itselfsorasto'protide a pairof spaced with the space th erehewee beanie wea ea stri f etflexible material lying between eech pair of 1 5 d l eiif lie t th' a tl l bbf 5 s are? 6. eng etl ug ii ll p y l o il saidst'ripsfand of thiii sheetf 'rnetal t upper ed e t e is he eri;

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